The Ancient Library is a site I have just found, thanks to Explorator. It contains out-of-copyright Classical reference works, at the moment:
- William Smith: Dictionary of Greek and Roman Antiquities
- William Smith: Dictionary of Greek and Roman Biography and Mythology
- Oskar Seyffert: Dictionary of Classical Antiquities
- William Hazlitt: Classical Gazetteer
There are six other books, including an English-Greek lexicon.
If the reference works are of necessity dated, the site has just begun a Wiki Classical Encyclopedia, which the Editor says will be to the Oxford Classical Dictionary what Wikipedia is to the Encyclopedia Britannica.
A Wiki, if you haven't come across it yet, is “a special sort of dictionary or encyclopedia that anyone can edit.” So the content will be as up-to-date as you, or I, or anyone out there, can make it.